1. Field of the invention:
The present invention relates to a torque variation absorbing device for an engine.
2. Description of the prior art:
An engine for an automobile or an aircraft is equipped with a torque variation absorbing device for power transmission.
The prior art offers such a torque variation absorbing device as disclosed, for instance, in Japanese patent publications Nos. SHO 55-020930, SHO 55-20964 and SHO 56-43176. Referring to FIG. 7, a device of the prior art has two inertia members, i.e., a driving plate 101 which is rotatably connected to a crankshaft of an engine and a flywheel 102 which is connected to the follower means and is rotatable with respect to the driving plate. Between the driving plate 101 and the flywheel 102, a spring mechanism 103 and a torque limiting mechanism 104 are installed. In this device the rotation of the crankshaft is transmitted to the flywheel 102 through the driving plate 101, the spring mechanism 103 and the torque limiting mechanism 104. Thus the torque variation is absorbed by the vibration system of these members. An oil drain hole 105 is provided at the inner portion of the flywheel 102. The hole 105 serves to drain the grease or oil 108 splashing from the clutch spline 106 and prevent the oil from reaching a clutch friction surface 107.
However, in the above-mentioned device, the torque limiting mechanism 104 is located radially outside of the spring mechanism 103 and radially outside of the oil drain hole 105. Therefore, oil flowing through the hole 105 can splash onto the torque limiting mechanism 104. The splashed oil may reduce the amount of transmitted torque and cause an undesirable slip. As a result, the vehicle becomes difficult to accelerate and its fuel efficiency drops.
Besides, in the above-mentioned device there is a straight gap 109 extending radially between the driving plate 101 and the flywheel 102. Therefore, the spring mechanism 103 and the torque limiting mechanism 104 are open outwardly. On account of this layout, foreign substance such as a wood chip can invade through the gap as the device is being transported or assembled and cause the performance of the device, and in the worst case, even its durability to deteriorate.
Further, the driving plate 101 of the device is made from a machined casting which is likely to include cavities. Therefore, the plate must be made thick in order to maintain the structural strength of the plate. Consequently, it was difficult to make the device compact.